Neither of my kids slept through the night until after their first birthday - most of the people I know with young kids experienced the same thing. And, we tried it all - keeping them up later, giving them "food" before bed, etc.
They still have relatively small stomachs, and if they're not incorporating more solids into their diet, they're burning through the milk so quickly.....just like how a Slim Fast or a Carnation Instant Breakfast doesn't last long for us as adults.
I'd take his cues and continue to nurse until he is showing signs that he doesn't need it. It won't be long before he's sleeping better, and you'll be getting a better night's sleep.
Good luck!